Buffered photographic film



Dec. 13, 1938. G. F. NADEAU 2,139,767

BUFFERED PHOTOGRAPHIC FILM Filed Feb. 15, 195e BUFFERED SUBLAYER BUFFERED BACKING ,ff r Bul-'repro u/vosleooAT BUFFERED ADHeswE u 1 INVENTOR:

GaleENadeeuu ATTORNEYS.

Patented Dec. 13, 1938 UNITED STATES PATENT OFFICE BUFFERED' PHOTOGRAPHIC FILM Jersey Application February 15, 1936, Serial No. 64,103

12 Claims.

This invention relates to photographic lms and particularly to a method of controlling the acidity of layers coated on the film which lmay exert an undesirable effect on the sensitivity of the emulsion.'

It is known that photographic emulsions are affected by change in acidity or hydrogen ion concentration and that a loss in speed or sensitivity results from the addition of acidic mam terial to the emulsion. In coating a sensitive material on the film base carrying subbing or other layers designed to protect it from, or cause it to adhere to, the base, the water of the emulsion leeches materials from the sub layers or f from the base. If the material leached out by the emulsion in this way has a dierent degree of acidity than the emulsion itself, the sensitivity of the emulsion is affected and a loss in speed or other undesirable result isprOduCed. These defects are usually manifested by lines or areas of varying sensitivity. If the acidity of the base is uniformly diierent from that ofthe emulsion, there may b e an over-all loss insensitivity which becomes very bad on ageing. There may also be a loss in the latent image or a loss in contrast on ageing for normal periods. When a gelatin subbin solution is applied to the film base priorv to coating the sensitive emulsion, the gelatin solution may be coated at a high temperature which tends to cause hydrolytic breakdown of the gelatin. This is accompanied by a drop in pH and a change in viscosity, due to the breaking down of the gelatin. As the pH drops, the accumulated acid catalyzes this hydrolytic breakdown and a condition of high acidity soon results which is communicated to the sensitive emulsion later coated on the base.

It is accordingly the principal object of the present invention to provide a photographic film 40 having the acidity of the layers which come in Contact with the sensitive emulsio-n so adjusted that the sensitive emulsion will not be adversely afected. A further object is to provide a stripping lm having the acidity of the adhesive 45 layer so adjusted that the speed and fogging characteristics of the sensitive emulsion are not aiected by it. A still further object is to provide a backing layer for a sensitive lm which has the acidity so controlled that it will not affect the sensitive emulsion when it is brought into which may come in contact with or alect the (Cl. -9l

sensitive emulsion to the pH of the emulsion and adding to it a buiering material to maintain it substantially at that pH.

In the accompanying drawing which is by way of illustration only,

Fig. 1 represents a single view of a lm having a buiered sub layer;

Fig. 2 is a sectional view of a film having a' buered undercoat between the layer and the emulsion;

Fig. 3 is a sectional view of a lm having a buiiercd backing layer;

Fig. 4 isa sectional View of a lm having emulsion layers and buffered undercoat layers on each side of the support; and

Fig. 5 is a sectional view of a stripping lrn having a buffered adhesive layer.

In carrying out my invention I add to the solution of the material which is to be coated on the lm base, a suitable amount of a material which has the required buffering action. This material may be a suitable acid salt or base salt mixture, or I may use a suitable water-soluble,

non-volatile, organic acid, such as oxalic, tartaric or succinic acid, in combination witha proper salt of said acid.

By acid salt mixture and base salt mixture I mean a mixture of an acid or a 'base with its corresponding salt, for example, citric acid and sodium citrate is an acid salt mixture, and am. monium chloride and ammonia is a base salt mixture.

It is sometimes necessary to add only an acid to buer against an increase in acidity, the inherent buffering capacity of the gelatin taking care of the buffering against an increase in alkalinity. For example, for pH ranges below about 5.5, gelatin and an added acid constitute an efcient buier by reason of the alkaline buffering capacity of gelatin in these pH ranges.

The action of buiering materials is well recognized and will not be reviewed here. It is to be understood that I may employ any suitable buering material in suilicient amount to obtain the desired result, it being only necessary that the material'be one which does not adversely aiect the sensitive emulsion.

Referring to the accompanying drawing which illustrates several methods of usingmy invention, Fig. 1 is a view in section of a dm comprising a support l0 which may be of cellulose nitrate coated with a buffered sub layer Il and having thereon a sensitive emulsion layer l2. Tlv/e buiered sub layer prevents the action of acids or other undesirable material in the base I0 from reaching and affecting-the sensitivity of .the

, sensitive emulsion4 I2. lIn Fig. 2 the base I0 is `in the layer. [Sforfthe base I0.

.ppse.' `Ai stripping film having coated with an'jordinary" gelatin sub layer I3 over which is coated a buffered gelatin layer III on which is laid the sensitive emulsion I 2. In the base of cellulose lacetate or other cellulose ester films frequently necessary j-to `coat several 4'gelatixror' other layerson the lmiIQSfecure ad'.- hesion. of. the sensitive emulsion-"layer, as illuswas 1n ng- Fi ."3 shows a section of ajlmcomprising the usual'support I0, sub layer I3 -and emulsion I2. This'lm has on-tlie back ther'efoifja gelatin layer I5 buffered to the pH of the emulsion I2 -so that when the lm is rolled Aand the layer JI5 congesff vinto contact with the layer I2 the sensitivity of the layer ,l2 willnot beaiected Fig. 4 .'shows'` ajiilm having an emulsion. ayer v I2 -anda buffered gelatinllayer I4 on each side'of asupport I0. 4There- 'in-'a'y also be an additional sub layer I 3 betweenthe support and the buffered lgelati-n layer, lalthough this layeris not essen-.-

tial -Other subbing layers may also be added.Y and there may be a layer .over the emulsion, such base during exposure and formation of the image and is removed from the temporary base during processing. These emulsions are usually of a type which produces an image of extreme contrast. The emulsion is supported on a permanent base, such as collodion or other cellulose derivative. which is ailixed t-fthf: temporary support by means of a water-soi' ale adhesive. Since the emulsion has a high degree of acidity and the adhesive us'ed to afx the permanent support carrying the emulsion layer to the temporary supportlusually has a lower degree of acidity. stripping lms previously made in this way have not been entirely satisfactory, due to the reaction between the emulsion layer and the adhesive layer, which resulted in spotting and logging of the emulsion. The permanent .emulsion support, moreover, must be ywater permeable so that the -water of the processing baths'can pass through it and reach the adhesive layer, For this reason' the permanent support shouldbe one which prevents' reaction betweenthe-.sensitive emulsion and the adhesive layer, 'and-.at the same time should be sufficiently 'water 'permeable to permit waterfto pass through i'tand reach the adhesive* layer; Another requisite of the permanent emulsion support is that it should-not swell or shrink duringl or after removal-f fromthe temporary support, since thisgdi's'tortsthe photographic image and makes it useless for its intended purthese `characteristics is-illustrated in Fig. 5 in which I6-.is a temporary support of paper o'r suitable material having a baryta coating l1. Over this is laid the adhesive layer I8 which is buffered to the pH of the sensitive emulsion.4 On the adhesive layer is coated the permanent support I9 of cellulose nitrate and on this is' a sensitive emulsion 20, and a gelatin coating 2| is ailxed to the opposite side of `the support I6.

by the- ..matena1s l to aboveisdetermined as follows: 10 grams of dry ',hesive layer.

should contain approximately 9% to' 12% of nitrogen. It will have a solubility in methyl alcohol of 30 to 100% and a viscosity of 2 to 5 secondsy by the dropping ball method. 'I'his cellulose nitrate should be water permeable in order to .permit the water of the developing or other treatment bathsto'rach and penetrate the adhesive 'layer'. vIn order' to increase this water permeability itis desirable to add certain materials,

suchfas glyceryl bori-borate, mono, diand triacetin,f.jlactic acid, glycerin, :various triethanolamine'iderivagtlves, ,lithium chloride, lithium nltrate, cadmium :bromide and' other materials. The nitrate may belpplied in asolution of rI1/2% s i'rnilar solvents.

lliscosityby the' dropping ball method referred :inC methyl alcohol, acetone andllbutyl alcohol or nitrocelllose-i-s` dissolved in cc. of a mixturecompiisi'ng 50% by volume of methyl alcohol and '5,0% 'by volume of acetone at 25 C.

Viscosity 4ismeasured by the time in seconds it f tak'siforfa steel ball having a diameter of Vath.

of an-,inch and Weighing .1320 gram to fall 15 'centimeters through the nitro cellulose solution at '25" C. in a tube having a diameter of 1.7- l-.05 centimeter.

The adhesive layer may consist of glue or liquid glue or a mixture of 'glue and dextrin. It is also possible to coat a layer of dextrin directly over the permanent support of paper or other material and to lay-the glue or glue and dextrin adhesive layer buffered to the proper pH on the dextrin layer. The glue solution may be plasticized with a solvent, such as glycerin, before applying it.

It is to be understood that while I have described a number of modifications of films having layers builiered according to my invention, I am not limited to films having the particular number or types of layers illustrated. Other layers may also be added, as for example, a gelatin overcoating upon the emulsion to prevent abrasion of said emulsion. Additional gelatiny subbing layers may be applied between the emulsion and the support or other gelatin layers may be applied over vthe sensitive emulsion layer or on the support, In the case of the stripping film a gelatin layer may be applied between the nitrate permanent support and the sensitive emulsion or between the nitrate permanent support and ad- The buffering backing layer may .contain a dye or other material which causes it to function as an anti-halation layer. The subbing layers may be composed of materials other than v'gelatin such as casein, agar, cellulose derivatives or resins.

The following embodiment, which is stated by way of example, is one method of forming a stripping lm according to 'my invention.

A porous type paper coated with clay or prei- .erably baryta is coated with a solution of glue sub is applied to the nitrate skin and tiel;4 is foly lowed by a sensitized silver-halide emulsion. The adhesive solution of glue is adjusted prior to coating to the hydrogen ion concentration of the emulsion by the addition of salicylic acid in the required amount, which may vary from 1A% to or more.

My invention contemplates the use of a large Among the buffering agents which I may use l are oxalic, tartaric, succinic, citric, maleic, cyanuric, salicylic, and diethyl barbituric acids. Boric acid may also be used in certain concentrations. 'Ihese are titrated to the proper pH by means of sodium hydroxide or some other suitable base.

It is to be understood that I am not limited in the examples given in the above specification but that my invention comprehends all modifications and equivalents coming Within the scope'of the appended claims.

What I claim as new and desire to 'secure by Letters Patent of the United States is:

1. A-photographic element comprising a support, a sensitive emulsion layer on said support,

`and a layer containing materials capable of producing a hydrogen ion concentration die'rent from that of the emulsion, said last mentioned layer being builered to a hydrogen ion concentration approximately the same as that of the emulsion.

2. A photographic element comprising a support, a sensitive emulsion layer` on said support,

and an intermediate layer between said support and said emulsion layer, said intermediate layer being buiered to a hydrogen ion concentration 4. A photographic element comprising a transparent support, a sensitive emulsion layer on said support, and a gelatin layerbetween said support and lsaid emulsion layer, said gelatin layer being buifered to a hydrogen ion concentration approximately the same as that of the emulsion.

5. A photographic element comprising a support, a sensitive emulsion layer on one side ,of said support, and a layer on the opposite side of said support, said last-mentioned layer being buffered to a, hydrogen lon concentration approximately the same as that of the emulsion.

6. A photographic stripping film comprising a temporary support, and as successive layers thereon, an adhesive layer, a water-permeable layer, and an emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration as the emulsion layer.

'7. Aphotographic stripping iilm comprising a temporary support, and as successive layers thereon, an adhesive layer, a Water-'permeable layer,

and a gelatin emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration as the emulsion layer.

8. A photographic stripping lm comprising a temporary support, and as successive layers thereon, a glue-containing adhesive layer, a Water-permeable layer, and an emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration as the emulsion layer.

9. A photographic stripping iilm comprising a temporary support, and as successive layers thereon, a glue and dextrin adhesive layer, a water-permeable layer, and an emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration Aas the emulsion layer. l l

10. A photographic stripping lm comprising av temporary support, and as successive layers thereon, an adhesive layer, a water-permeable cellulose nitrate layer, and an emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration as the emulsion layer.

11. A photographic stripping lm comprising a temporary support, and as successive layers thereon, a glue-containing adhesive layer, a water-permeable cellulose nitrate layer,f and an p emulsion layer, the adhesive layer being buieredv to substantially the same hydrogen .ion concentration as the emulsion layer.

12. A photographic stripping iilm comprising a temporary support, and as successive layers thereon, an adhesive layer, a water-permeable cellulose rnitrate layer, and a sensitive emulsion layer, the adhesive layer being buffered to substantially the same hydrogen ion concentration as the emulsion layer.

GALE F. NADEAU. 

